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Startup Runway Calculator

Hope is not a strategy. Math is.

Startup runway is how many months your cash lasts at your current burn: cash divided by net monthly burn. With €120,000 in the bank and €8,000 net burn a month, you have 15 months of runway. If revenue grows fast enough to cover costs first, you never run out and you are Default Alive.

How it works

Enter your Starting Cash and current MRR.

Project your Revenue Growth (be honest).

Factor in Expenses and their growth.

See if you are Default Alive or Default Dead.

Why it matters

Most founders calculate runway by dividing cash by burn. That's wrong because it assumes zero growth.

This tool models the dynamic relationship between growing revenue and growing costs. It tells you the exact month you run out of money, or the moment you become profitable.

The Math

Net Burn = Expenses - Revenue
Cash(t) = Cash(t-1) - Net Burn(t)
Alive = Cash never hits 0.

How it's calculated

The quick version is cash divided by net monthly burn, which gives you the months of runway left at a flat burn. The trouble is that burn is rarely flat. As revenue grows, your net burn shrinks, so the simple formula understates how long you really have.

That is why the tool projects each month forward. It asks the question Paul Graham made famous: are you Default Alive or Default Dead? Default Alive means that, on your current growth and spending, you would reach profitability before the cash runs out, without raising again. Default Dead means the money runs out first. The sooner you know which one you are, the more options you still have to change it.

Worked examples

Cash Net monthly burn Runway
€50,000 €5,000 10 months
€120,000 €8,000 15 months
€500,000 €25,000 20 months
CALCULATING...
Enter your numbers to see your fate.

Questions people ask

How do you calculate startup runway?

Divide the cash in your bank by your net monthly burn (expenses minus revenue). If you hold €120,000 and burn €8,000 net per month, that is 15 months of runway. This assumes a flat burn. If revenue is growing, the real number is higher, because each month your net burn shrinks and your cash lasts longer.

What is a good runway?

A common rule of thumb is 18 to 24 months of runway after a raise. That gives you roughly a year to hit the milestones for your next round and a few months of buffer to actually close it. Below 6 months you are in the danger zone and should be cutting costs or raising already.

What does Default Alive mean?

Default Alive is Paul Graham's term for a startup that, on its current growth and spending, would reach profitability before the money runs out, without raising again. Default Dead is the opposite: the cash runs out first. Knowing which one you are, early, is the single most useful number a founder can track.